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The good lubrication of the gears is also directly related to the additives of the oil. For example, an oily additive is added to the lubricating oil, and the active molecules of the oily additive can be relatively firmly adsorbed on the tooth surface of the tooth, and the contact of the peak point is prevented by the adsorption oil film to maintain good lubrication of the tooth surface. For example, the common worm gear drive can not achieve fluid dynamic pressure lubrication. After adding the oil additive, the lubrication state can be changed. For another example, when the tooth surface load of the gear teeth is excessively large, the boundary lubricating oil film is broken. In order to prevent dry friction, an extreme pressure antiwear additive may be added to the lubricating oil. This additive reacts with the tooth surface to form an extreme pressure lubricant film that protects the tooth surface and prevents dry friction and wear.
The relationship between gear damage and lubrication Adhesive wear Adhesive wear is the most common wear phenomenon of gears. It is produced because the tooth surface generates more heat when sliding at a higher speed, causing the viscosity of the oil to drop, and finally causing the oil film to rupture. After the oil film breaks, the tooth surface directly rubs and welds, and in the continued sliding, the lower strength metal is torn from the tooth surface, and the wheel surface is damaged. Adhesive wear is a sign of insufficient lubricant carrying capacity or gear overload.
When it is light, the tooth surface is scratched or scratched. When it is severe, it is pulled into a deep groove and a pattern of overheating occurs, thereby reducing the hardness of the tooth surface and sometimes even causing damage to the entire tooth. The viscosity of the oil is closely related to the thickness of the oil film. The greater the viscosity of the lubricating oil, the thicker the oil film on the tooth surface, and the less the adhesion wear is less likely to occur. Therefore, the use of high-viscosity lubricating oil (referring to gears driven at low speed) has a positive effect on preventing the adhesion and wear of the tooth surface. For high-speed transmission gears, due to their high linear speed, lubricants with low viscosity should be used to reduce the resistance during transmission.
The relationship between the viscosity of the lubricating oil and the thickness of the oil film is pitting in the gear transmission, and pitting corrosion is also extremely common. This general form of surface fatigue occurs as a result of high loads causing excessive stress on small areas of the gear surface. When this happens, after repeated cycles, cracks appear inside the surface and then spread to the surface, and when a piece of material cannot be supported, it leaves the surface of the tooth, resulting in small pits. When the bumps left by the machining are removed, the small pits are formed on the new gear. Once the area of ​​contact is sufficient to support the load, pitting may stop and the surface begins to polish, and if this occurs, the initial pitting may be considered harmless.
The viscosity of the lubricating oil has a large influence on the pitting of the gear. For example, low-viscosity oil is used to lubricate gears. Although low-viscosity lubricating oils have good flow properties and are easy to penetrate into surface cracks, when subjected to high-pressure contact stress, oil generates high pressure in cracks, thereby accelerating crack development and metal. If the block falls off, it will cause pitting; on the contrary, it will be lubricated with high-viscosity oil. The effect of penetrating cracks is obviously no low-viscosity oil, and the oil film thickness is large, thus alleviating the impact load and homogenizing the contact stress. The ground reduces the maximum stress value, thereby increasing the resistance of the tooth surface to pitting corrosion.
In addition to the main forms described above, the damage of the gears is also broken, abrasive wear and corrosion wear. Several methods for selecting gear lubricants 2.1AGMA standard specification "Lubrication of industrial closed gear transmissions" uses empirical data to select the gear oil type and viscosity used for gears. A typical example in this regard is the American Gear Manufacturers Association AGMA standard. Table data on the lubrication of industrial closed gear transmissions in the specification.